Islamabad: Seven persons, including two policemen, were killed on Thursday in two separate incidents of violence in Pakistan's restive northwest, adding to concerns about security ahead of next month's general election.

Two policemen and four militants were killed in a fierce shootout in Karak district of Khyber-Pakhtunkhwa province on Thursday morning, police officials said. Three more policemen were injured in the skirmish.

Acting on a tip-off about the presence of militants in Banda Daudshah area, police launched a search operation. The militants began firing indiscriminately once police arrived at the spot.

A police officer and a constable were killed instantly. The injured policemen were taken to a nearby hospital. The gun battle continued for several hours and both sides used automatic weapons. Policemen conducted a sweep in the area after the shootout.

In a separate incident, a tribesman was killed and three more were injured when a landmine exploded near a sports complex in Parachinar, the main town of the restive Kurram tribal region.

Officials of the region's political administration said the blast occurred when a tractor-trolley ran over the landmine. The injured were taken to a hospital in Parachinar.

Northwest Pakistan has witnessed a spike in violence ahead of the May 11 general election, which will mark the country's first democratic transition of power. The banned Pakistani Taliban have threatened to target leaders and rallies of the secular Awami National Party, Pakistan People's Party and Mutthida Qaumi Movement.